


Slow Grind

by Eiznel24



Category: Undertale (Video Game)
Genre: Frottage, M/M, Sensitive bones, Wall Sex, kind of
Language: English
Status: Completed
Published: 2017-09-03
Updated: 2017-09-03
Packaged: 2018-12-23 07:04:22
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,848
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11984670
Author URL: https://archiveofourown.org/users/Eiznel24/pseuds/Eiznel24
Summary: It's the 5th annual celebration of returning to the Surface, and Sans had been avoiding him for so long. A little push from his captain, and Papyrus decided to take fate into his own hands.





	Slow Grind

It all felt a little surreal, Alphys quietly thought to herself. Ever since she’d been small, she’d dreamed of seeing the surface…like everyone else, she huffed to herself with a quick roll of her eyes. And now five years had passed. Five years of living on the surface. Two years of being married to Undyne, she added with a fierce blush. She remembered how uncharacteristically flustered the tall monster had been, and smiled softly when she recalled how wide Undyne’s grin had been when she said yes. She felt so lucky…she wished everyone could feel the same kind of happiness she did. Especially those two, she thought with a sigh.  

She watched as Undyne hooked an arm around Papyrus’s shoulder and said something to him, then laughed riotously with a smack to his back. Papyrus laughed even louder than her, trying far too hard to share in Undyne’s humor when Alphys could clearly see that his mind was somewhere else, his eyesockets constantly drifting to the right. Without even having to look, she knew that’s where Sans was. And she could probably bet a handful of gold that Sans was studiously looking away and trying so hard to play it casual when all he wanted was to be near Papyrus.  

She wasn’t sure why they were keeping away from each other like this; she’d tried asking Sans about it when she noticed the shorter brother wasn’t standing as close to Papyrus as he used to. Sans had shrugged lightly with a widened grin and said that Papyrus needed room to grow and become his own monster. 

 _‘He doesn’t need that,_ _yo_ _u_ _silly skeleton. He needs_ you _! Ugh, what do I need to do to get him to see that?’_  

Alphys looked back at her wife and hummed thoughtfully. She wasn’t good at speaking up, but maybe Undyne could fill that role? Orrrr maybe she wouldn’t need to, she realized, as she saw Undyne narrow her eye at Papyrus and grab his arm, pulling him aside and saying something she couldn’t hear. Alphys turned around and smiled a tiny smile, her clawed hands coming together in a way that one could mistake for prayer. Maybe they could use a prayer, she mused with a giggle. They could use all the help they could get. 

 

* * *

 

 

“What’s going on with you? You’ve been a space-case for a while and it’s only gotten worse! What gives, punk?” 

Undyne noticed the way he flinched slightly at “space-case” and she frowned sharply when he waved his hands and grinned widely. 

“OH IT’S NOTHING, UNDYNE! I’VE SIMPLY HAD MANY A RECIPE IN THIS THINK FACTORY OF MINE! ONE CAN NEVER STOP PURSUING PERFECTION, AM I NOT CORRECT?” 

“Cut the shit, Papyrus.” 

“E-EXCUSE ME?” he exclaimed, his grin fading and his jaw dropping a little. 

“You’re not fooling me, you little turd,” she snarled. “Something’s bothering you, and as your best friend, I demand to know what it is!” She looked down to the side, then back at him, the nearly glowing yellow eye cutting through Papyrus’s defenses. Her voice was lower, almost wounded. “Do you not trust me or something?” 

Papyrus flinched again and she saw tiny beads of sweat develop on his skull. He waved his hands one more time. 

“I-IT’S NOT THAT AT ALL. I TRUST YOU WITH MY LIFE, UNDYNE! AND YOU’RE MY BEST FRIEND, TOO!” One hand dropped and wrapped around the humerus of his opposite arm. “I JUST…it’s not a simple matter?” 

Undyne watched his eyesockets dart to the right and a small blush develop on his cheekbones. Some of her anger dissipated. 

“Oh, so this is  _that_  kinda issue, huh?” She turned her head a little to see why Papyrus kept glancing to the right and understanding dawned as she saw Sans standing near a group of monsters (patrons from Grillby’s, maybe?), his hands in his black shorts. The small group laughed at something he said and his shoulders bounced once in what she could assume was a laugh. 

“Wait, why haven’t you told him anything?” 

Papyrus said nothing for a second, and she turned back to him just in time to see the intense longing on his face before he covered it with an annoyed expression. 

“I HAVE. HE SAID WE COULDN’T, THAT IT WAS AGAINST THE RULES.” He scoffed, his arms crossing against his chest, the soft white fabric of his dress shirt bunching together. “SINCE WHEN HAS SANS FOLLOWED RULES? AND WHAT RULES ARE THESE, ANYWAY!? I HAVEN’T SEEN THEM!” 

He went silent again, and when he spoke the irritation was missing from his voice. “Ever since then, he’s done his best not to be alone with me for too long. I don’t think he wants to talk about it. There have been a few occasions where I wish I had said nothing at all.”  

A quick strike landed near his shoulder and he yelped, raising a hand to rub at the sore spot. His eyesockets locked with Undyne’s yellow eye and she was glaring at him, challenging him, her own white dress shirt pulled taut as she crossed her arms and flexed her muscles. 

“No regrets, Papyrus. When the hell have you ever been the kind of monster to back down from a problem? That idiot should know by now that we’d all support you. Go talk to him, beat some sense into him if you have to. Papyrus never loses! Right!?” 

Tears welled in Papyrus’s eyesockets as he stood straight and saluted Undyne, a grin forming. Undyne grinned back and saluted as well.  

“Go get ‘im, champ!” 

“YES, MA’AM!” 

 

* * *

 

 

Stars above, he was beautiful, Sans thought to himself as he took a surreptitious glance at Papyrus. He was far subtler than Papyrus was, always making sure no one else was looking when he decided to sneak a peek. His eyelights made a quick drag down Papyrus’s form. The soft white dress shirt, which Toriel had given him last Gyftmas, hugged his form well, the sleeves carefully folded to the elbows. The tie had been a gift from him, a muted black silk with skull and crossbones highlighted in purple with one eyesocket larger than the other. It had instantly reminded him of Papyrus when he had seen it and had known it would be the perfect gift to go with Toriel’s. Black slacks fell  _just_   _right_  down his legs and ended in slick ankle-length dress boots with silver buckles that could just barely be seen beneath the hem. He deliberately saved his hands for last. Supple black leather gloves covered Papyrus’s long fingers, and the more depraved part of Sans (which he shoved down violently) wished he knew exactly how they would feel against his bones.  

A knot formed where his throat would be when he saw the bones beneath Papyrus’s shirt shift as the tall monster crossed his arms. Sans turned away, his soul skipping as he tried not to let his breathing quicken. He had been doing so well… 

At first it had been easy to put aside his attraction for his brother. Papyrus was a ball of energy, hyper-focused on getting into the Royal Guard and capturing humans. Papyrus had just been Papyrus, the brother that Sans loved dearly and would protect above anything else. Any fleeting thoughts of how attractive he was or much he wanted to get closer were ignored. Then they reached the surface and everyone’s attentions were put toward establishing a new home, toward getting into the swing of a new life. Things had been okay then, too. 

Then sometime after Alphys and Undyne’s wedding, Papyrus had started getting too close for Sans not to notice. He had asked what Papyrus was doing when their fingers brushed together while watching TV and the skeleton had become a blushing stammering mess, and had blurted out his feelings. In an ideal setting, Sans would be overjoyed, but he was not, and it was not. Papyrus was his brother, the skeleton who already had an absurdly difficult time making friends. Surely dating one’s own brother would only make finding friends even more difficult?  

And Papyrus was so sweet, while Sans was most decidedly not. He was gross, and horrible, and wanted to do horrible things to his beautiful bro…or have horrible things done to him, he wasn’t picky. So he turned Papyrus away, and made sure to keep his distance. Keep it civil, he’d tell himself. Make sure it stays brotherly. But stars, he loved the way Papyrus looked at him and he always felt a pang in his chest (and his crotch, if he was honest) that he couldn’t allow himself to get closer. Oh, how he wanted to… 

“What ever is the matter, dearie? You look absolutely  _caught up_  in something! Uhuhu!” 

Sans looked up at Muffet and grinned lightly. “that was smooth as  _silk_ , muffet. didn’t know ya could  _spin_  your words so well.” 

There was a smattering of chuckles around him and his shoulders bobbed once as he gave a short laugh.  

“nah, i’m alright. just got a few  _webs_  up in my noggin that need cleanin’ up.” He brushed a few stray crumbs off his tuxedo print shirt and put his hands back in his pockets. He wasn’t fond of lying, he mused with a frown, but he had no other choice. Sans straightened from his slouch when he heard a yelp coming from Papyrus’s direction, but forced himself to relax again. Papyrus was with Undyne; they were likely just playing around. Why was he thinking about him so much all of a sudden? He growled to himself and had to resist rubbing his face in irritation. When was he  _not_  thinking about Papyrus? There was hardly a moment where his thoughts weren’t centered around him. Damn it. 

“YES, MA’AM!” came the shout from across the room above the buzz of the crowd, and he chuckled. Ever the dutiful soldier…or would-be soldier, such as the case may be. The group near him dispersed and he raised a brow ridge in confusion. Why would they--? 

“SANS.” 

Fuck. 

He turned around casually, smiling as easily as he could. 

“hey, what’s goin’ on, paps?” 

The smile dropped when Papyrus’s gloved hand wrapped around his wrist. He desperately tried not to shiver. 

“I MUST INSIST WE SPEAK PRIVATELY.” 

He tugged lightly against Papyrus’s hold. 

“uh, can it wait? there’s still a lotta people we gotta talk to before the night’s over.” 

Sans’s eyelights fixed on Papyrus’s sockets and he gulped at the serious look there. 

“IF I SAY YES, YOU WILL FIND A WAY TO AVOID ME FOR THE FORSEEABLE FUTURE. SO NO, SANS, I WILL NOT WAIT.” 

“i…okay.”  

He supposed it was going to happen sometime, but he wasn’t expecting such a public area for Papyrus to become stubborn. Quietly, he followed Papyrus towards the front door of the hall they were renting for the night. A soundless sigh flowed past his teeth as the cool breeze of the evening brushed against his bones.  

Papyrus turned around and faced Sans, his arms crossed and the index finger of his right hand tapping against his arm (which Sans tried not to focus on). For a long moment, silence dragged on between them and Sans was reminded of a pissed off spouse waiting for an explanation. He refused to continue that line of thought. Before Sans could finally break the silence, Papyrus’s hands flew up to his skull and he began pacing in a short circuit. 

“ARGH! WHY ARE YOU SO STUBBORN!?” he shrieked, echoing Sans’s earlier thoughts of  _him_. 

“…what?” 

A gloved finger was shoved in his direction and Sans squashed the desire to pull on it and make a farting noise. 

“YOU’VE BEEN AVOIDING ME!” 

“have i?” 

“YES! EVER SINCE I REQUESTED YOU DATE ME, YOU’VE SCARCELY BEEN AROUND!” 

“you kinda demanded i date you, not ask.” 

“IS THERE A DIFFERENCE?” 

“a bit.” 

Papyrus frowned and put his hands on his hips. 

“WELL, WILL YOU PLEASE DATE ME?” 

“no.” 

“WHY NOT!?” 

Sans sighed and ran a hand over the top of his skull, his sockets falling shut. 

“paps, we’ve been over this.” 

“NO, WE HAVEN’T.” 

“…whaddya mean, we haven’t? i kinda made it very clear when you approached me the first time that it’s not a good idea.” 

“WE HAVE DISCUSSED YOUR SIDE OF THE MATTER. NOT MINE.” 

His side? 

“what’s that supposed to mean?” 

“OUR FRIENDS WOULD SUPPORT US. THEY FIND NOTHING WRONG WITH US BEING BROTHERS. LOVE IS MORE IMPORTANT THAN ANYTHING, REMEMBER?” 

“are you going to be satisfied with just them being happy with it? paps this isn’t just some thing you can jump into with no regard for the consequences.” 

Papyrus took a step toward him and he took a step back, needing to keep his distance. He could smell the ridiculous MTT cologne he wore from here and it was doing funny things to his insides. The topic did nothing to help the matter. Papyrus looked so amazing when he was serious… 

“THEY DON’T MATTER. NONE OF THEM DO. THEIR SUPPORT IS NICE, YES. BUT NONE OF THEM MATTER EXCEPT FOR US. IT’S  _OUR_  RELATIONSHIP, NOT THEIRS.” 

He could feel himself beginning to panic. Why was he panicking? This was good, wasn’t it? 

“you say that now. but it will get to you later. you’ll want to brag about us or something and when you’re hit with all the disapproval, it’s going to hurt, and you’re going to doubt everything.” 

…oh. He couldn’t remember the last time he’d seen a genuine frown on Papyrus’s face. 

“DO YOU REALLY THINK I’M THAT SUPERFICIAL?” 

Shit. Fuck. Damn it. 

“n-no! it’s just…i just…” 

“YOU WHAT?” 

Papyrus was too close. He smelled too good, he looked too good, what he was offering was too good… 

“you’re…you need to back up a bit, paps. i’m havin’ trouble thinkin’ straight with you so close.” 

Instead of backing up the way he wished Papyrus would, he heard more than saw Papyrus get closer. His voice was lower, softer, and it made Sans’s breath hitch. 

“…Why?” 

He knew he was blushing, he knew he probably looked like a wreck and Papyrus hadn’t even touched him, hadn’t even said anything. Sans looked up and saw that a low blush was covering Papyrus’s cheekbones, too, and he felt his soul skip again. 

“you…fuckin damn it, i want you so much and you look way too good for my sanity and i’m probably already crazy…” he felt himself beginning to ramble and cut himself off, his breathing shaky. 

“You want me?” 

“i…” 

The door opened and Sans jumped backward, his back hitting the wall. A monster he could foggily place as Burgerpants walked out, a cigarette between his fingers. He turned lazy eyes to them and pointed a thumb back at the hall. 

“The dancing has started, buds. Pretty sure my boss would hang you by your toes from a light pole if you missed out on it. Napstablook’s the DJ.” 

Good, an opportunity to clear his head. Sans started walking for the door. 

“ah, best not miss it then. let’s head back in, shall we?” 

With a noise of displeasure, Papyrus followed, keeping his sockets glued on Sans as they weaved through the now active crowd. A lively tune with a heavy beat was just wrapping up and as they moved into the heart of the dance floor, Sans put more space between them. Or at least, he attempted to. A heavier song came on, one with a beat that almost felt dirty and left Sans unintentionally flicking his eyelights over to Papyrus, who was still watching him. He could tell that Papyrus was desperately trying to remain calm, but he could tell that he was nervous about something. The tall skeleton held out his hand. 

“DANCE WITH ME.” 

Almost immediately, Sans was shaking his head. 

“uh…dancin’ ain’t really my thing, paps.” 

Papyrus’s hand latched onto his anyway with a movement that was a little too quick to be casual. 

“THEN STEP OUTSIDE YOUR COMFORT ZONE FOR A BIT,” Papyrus declared in a voice that was more confident than he felt. 

“…okay.” 

Papyrus seemed to be concentrating on something with the way his sockets had moved from Sans to train on the floor. His gloved hand slid up Sans’s arm and the other hand mimicked the movement, drawing the shorter skeleton closer.  

“u-uh…” 

“Put your arms around my neck,” Papyrus directed, and blushed when Sans did, but shook his head with some sort of inner conviction and dragged his hands to Sans’s hips. There was still a respectable distance between their chests, but they were a little closer near the hips than Sans wanted to contemplate. His train of thought stuttered when Papyrus bent his knees a little and began gyrating both of their hips in time with each other, but in opposite directions. 

“wh-wh-what are doing?” Sans sputtered. 

“Grinding,” Papyrus stated, as if it were the most obvious thing in the world. 

“where did you learn this!?” 

“YouTube.” 

“wh…hhh….” 

Sans’s knee was between Papyrus’s legs and he was just thinking of all the different things they could be doing to each other if there was no one else around. They weren’t even dating; he shouldn’t be thinking like this. He shouldn’t. He-- 

“Turn around,” Papyrus murmured. Cyan flared up on Sans’s cheeks like a beacon and he jerkily did as Papyrus requested, his hands curling in tight fists and hovering a little awkwardly in the air in front of him. He was dragged even closer and felt Papyrus begin to guide him in swaying movements. His hands flew down to grip Papyrus’s, his breath coming in short gasps.  

Sans’s mind was going to short-circuit. Their pelvises were almost touching… oh god, they were in public. He shouldn’t be getting so excited. His eyelights raised in a panic, but he found no one was even looking at them, completely absorbed in the music or their dancing partner. He caught a glimpse of Undyne and Alphys between two other couples and saw Undyne grin sharply in their direction, then turn back to focus on her wife. 

This time, he felt their pelvises touch, and a small noise escaped him despite his best effort. Papyrus’s skull came down to tuck itself into his shoulder, and he could hear the labored breath coming from the taller skeleton. Sans raised one arm to cup the back of Papyrus’s skull, and the other reached behind him to grab Papyrus’s hip. In response, Papyrus practically molded their bodies together and continued their movements.  

“oh god,” Sans moaned softly, his eyes shut. 

“Sans,” Papyrus called softly, his voice strained. 

For a moment, Sans couldn’t respond, too focused on the feel of Papyrus grinding into his sacrum. 

“hah…yeah…?” 

“I want you too,” came the soft whine. 

And just like that, all of Sans’s reservations shattered and desire flooded him like a shockwave.  

“fuck…”  

His grip tightened on Papyrus and Papyrus reciprocated. 

“we need to go.” 

“Yes, we do.” 

As soon as the words were past Papyrus’s teeth, they were inside their house and Sans had flipped around in Papyrus’s grip, grabbing his tie and dragging him down for a kiss. Papyrus only made a slight noise of surprise before latching onto him with equal fervor, peppering kisses all along Sans’s skull. Before Sans could even begin to reciprocate, he found himself being lifted and slammed against their front door, hands gripping tightly against his hips. His legs automatically wrapped around Papyrus and he felt his mind go blank when he started feeling Papyrus nip along his neck and down to his shoulder. Those gloved fingers had slipped beneath the waistband of Sans’s shorts, pulling them down slightly and exposing the iliac crests, where he was rubbing circles into them.  

“n-nngh…paps…” 

He felt Papyrus shudder above him and groaned when their pelvises ground against each other. 

“S-say…say my name like that again.” 

A white-hot bolt of arousal shot through him hearing Papyrus’s voice so turned on, so rough. 

“papyrus-sah ahh!” he trailed off with a yelp as Papyrus started grinding against him more energetically. The friction of their clothes, of everything, of Papyrus’s harsh breath on the side of his skull, of the leather-clad fingers digging into his hips (feeling as delicious as he had hoped it would be), was all driving him mad. He started moving in turn, his hands gripping Papyrus’s shoulders in a vice. He dug his heels in, adding pressure to Papyrus’s sacrum and he felt the breathy moan reverberate in his skull.  

“Oh S-Sans…” 

Sans tilted his head up, his mouth falling open in a long, low moan. One of his hands trailed up and scraped along the back of Papyrus’s cervical vertebrae and he got a gasp and a sharp jerk of the hips as a reward. He could feel magic racing along his bones, making him feel like one giant livewire. Between all the sensations he was experiencing, he barely noticed Papyrus’s right hand begin to move, further pulling down Sans’s shorts and one adventurous thumb brushing against his pubic crest.  

His mind abruptly went blank and he could vaguely register that he was letting out a series of loud moans, far too focused on the blinding pleasure he was feeling. The thrusting became more of a slow roll and he heard Papyrus softly chanting his name like a prayer. Sans could feel his body tensing, grabbing onto Papyrus more tightly, his moans sounding almost like sobs at one point. The thumb rubbing at his pubic arch was steady, insistent, deliberate and he heard Papyrus’s words change as his body began to shake. 

“I love you, I love you, I love you, I love you---” 

Sans’s breath caught in his throat and Papyrus’s name was a strangled whisper that fled him as he came undone, his vision briefly going black. His body was crushed to his brother’s as Papyrus jerked unevenly, his own orgasm rapidly approaching. With shaky breaths, he reached up and pulled Papyrus’s head back so that their foreheads were touching. 

“come for me, bro.” 

And with a soft whine, Papyrus let go, ceasing his movement and trembling in place with the force of his orgasm. For moments after, they stayed there against the door, their foreheads still together and Sans’s fingers gently tracing patterns against Papyrus’s skull. Sans was the one to speak first. 

“…i love you, too. i always have.” 

Papyrus smiled, then laughed softly after a few seconds. 

“Confessions and dating were supposed to come  _before_  this, I’m pretty sure.” 

Sans was quiet for a moment, then laughed as well. 

“probably. but the order doesn’t matter if the result is the same, right?” 

There was a sharp pinch at Sans’s hip and he yelped before laughing again. 

“Perhaps. Perhaps not. But.” 

Papyrus nuzzled Sans’s cheekbone and gave him a mock stern look. 

“You’d better  _never_  make me chase you again.” 

Sans’s smile was cheeky. 

“isn’t half the fun the chase?” 

Another pinch was his response. 

**Author's Note:**

> This fic is dedicated to TrousledBones - Thank you for being a source of inspiration, of encouragement, of laughs, and endless shitposts. I value you more than you can ever know and probably wouldn't be posting more work without you.
> 
> First fic in quite some time; hope I'm not too rusty!


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